The in vivo dissolution of tricalcium silicate bone cement

This study aimed to investigate the in vivo dissolution of tricalcium silicate (Ca₃ SiO₅ , C₃ S) bone cement in the rabbit femoral defect. Results indicated that C₃ S paste directly integrated with the bone tissue without the protection of the bone-like apatite. Calcium silicate hydrate gel (C-S-H gel) and Ca(OH)₂ were the main components of C₃ S paste. The dissolution model of C₃ S paste was a mass loss rather than a decrease in volume. The initial dissolution of C₃ S paste (0 ~ 6 weeks) was greatly attributed to the release of Ca(OH)₂ , and the later dissolution (>6 weeks) was attributed to the decalcification of C-S-H gel. Although the mass of C₃ S paste could decrease by more than 19 wt % after 6 weeks of implantation, the created pores (<1 μm) were not large enough for the bone tissue to migrate into C₃ S paste. The loss of Ca ions also resulted in the transformation of SiO₄ tetrahedrons from Q¹ and Q² to Q⁰ , Q³ , and Q⁴ in C-S-H gel. Because only isolated SiO₄ tetrahedrons (Q⁰ ) and Ca ions could be absorbed by the bone tissue, C₃ S paste gradually transformed into a silica-rich gel. The fundamental reason for no decrease in volume of C₃ S paste was that the SiO₄ tetrahedron network still maintained the frame structure of C₃ S paste during the implantation.